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MythPlayer: Fix a Live TV channel change deadlock.

This recognises that the decoder loop effectively has 3 different states
- running, partially paused and completely paused. The partial pause
state still allows the playback thread to decode a single frame on
demand, seek and perform position map syncs. Allowing these while the
decoder is changing adds various complications - hence add a new member
state variable, totalDecoderPause, that ensures the decoder loop does
nothing other than check its own pause state when completely paused.

Aside from fixing a deadlock on channel changes, this should also
speedup decoder changes under certain situations and probably prevents a
couple of even more obscure bugs (e.g. if a seek is triggered at the
same time as a channel change).
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1 parent 1650de3 commit c42834e19857c4e79bd5600bd7c1768f34072d1d mark-kendall committed Apr 17, 2011
Showing with 12 additions and 1 deletion.
  1. +11 −1 mythtv/libs/libmythtv/mythplayer.cpp
  2. +1 −0 mythtv/libs/libmythtv/mythplayer.h
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12 mythtv/libs/libmythtv/mythplayer.cpp
@@ -130,7 +130,8 @@ MythPlayer::MythPlayer(bool muted)
parentWidget(NULL), embedid(0),
embx(-1), emby(-1), embw(-1), embh(-1),
// State
- decoderPaused(false), pauseDecoder(false), unpauseDecoder(false),
+ totalDecoderPause(false), decoderPaused(false),
+ pauseDecoder(false), unpauseDecoder(false),
killdecoder(false), decoderSeek(-1), decodeOneFrame(false),
needNewPauseFrame(false),
bufferPaused(false), videoPaused(false),
@@ -2836,6 +2837,12 @@ void MythPlayer::DecoderLoop(bool pause)
{
DecoderPauseCheck();
+ if (totalDecoderPause)
+ {
+ usleep(1000);
+ continue;
+ }
+
if (forcePositionMapSync)
{
if (!decoder_change_lock.tryLock(1))
@@ -4573,6 +4580,7 @@ bool MythPlayer::SetVideoByComponentTag(int tag)
*/
void MythPlayer::SetDecoder(DecoderBase *dec)
{
+ totalDecoderPause = true;
PauseDecoder();
{
@@ -4589,6 +4597,8 @@ void MythPlayer::SetDecoder(DecoderBase *dec)
}
decoder_change_lock.unlock();
}
+
+ totalDecoderPause = false;
}
bool MythPlayer::PosMapFromEnc(unsigned long long start,
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1 mythtv/libs/libmythtv/mythplayer.h
@@ -545,6 +545,7 @@ class MTV_PUBLIC MythPlayer
QWaitCondition decoderThreadUnpause;
mutable QMutex decoderPauseLock;
mutable QMutex decoderSeekLock;
+ bool totalDecoderPause;
bool decoderPaused;
bool pauseDecoder;
bool unpauseDecoder;

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